This invention relates to fountain pens and more particularly to a fountain pen equipped with a device by which the resiliency of the pen can be continuously adjusted.
If a hard resiliency is imparted to a writing pen point, the width of a line written therewith is uniform or is varied only according to the direction of writing. On the other hand, if the pen point has a soft resiliency, the width of a line written therewith is also varied according to variations in writing pressure which occur during writing.
It has long been felt desirable to be able to vary the resiliency of a pen point thereby to change the writing conditions so that one can produce both kinds of handwriting with one fountain pen. As an example of a prior art construction, in German Pat. No. 735131, a cylindrical member is positioned around the nib of a fountain pen with a surface contact portion provided at the end portion of the cylindrical member in such a manner that it is in contact with a portion of the nib. The resiliency of the pen point may be varied by the position of the surface contact portion. In order to provide satisfactory writing properties, the pen body has a curved configuration which varies over the entire pen from base to the top. That is, the pen body is not of uniform curvature. Therefore, if the resiliency of the pen is changed by moving the cylindrical member while the latter is depressed directly against the nib, the configuration of the pen is greatly changed. In this case, far from producing a usable resiliency variation, one cannot write with the pen. Accordingly, it is impossible to provide satisfactory fountain pens according to this patent document. In fact, so far as is known, such fountain pens have never been manufactured.
In a fountain pen disclosed by German Pat. No. 819054, a retaining metal member is brought into surface contact with the pen nib to change the resiliency of the pen. For the same reason as described above, such a pen has fatal detects which render it unfit for practical use.
In German Pat. No. 737672, a retaining metal member is placed in surface contact with the pen and writing pressure is exerted on the pen by manual pressure on the retaining metal member without moving the position of the retaining metal member in order to vary the handwriting. According to this technique, if the pen point itself is deformed by pressure, then one cannot satisfactorily write with the pen. In order to provide satisfactory writing conditions, the configuration of the pen body must have a predetermined curved configuration and the pen be readily deformable because of the material used for the body. Accordingly, only a low pressure may be applied to the pen to the extent that the pen is not deformed thereby. However, with such a low pressure, the handwriting can be only little varied. It is impossible to produce a practical fountain using this technique and, as before, such fountain pens have never been manufactured and used commercially.
U.S. Pat. No. 881,215 discloses a fountain pen in which a retaining metal member is held in contact with the pen nib with the nib held tightly against the core. The text of the patent states nothing about varying the resiliency of the pen. The fountain pen disclosed by this patent is further disadvantageous in that, as the retaining metal member is moved, the ink would be expected to seep into the holder cylinder and the retaining metal member is laterally displacable because no guide for the retaining metal member is provided. Furthermore, the fountain pen is disadvantageous in that, since the pen nib is in surface contact with the portion other than the end portion of the retaining metal member, the retaining metal member cannot be moved when the ink between the pen and the portion of the retaining metal member is dried. Thus, such a fountain pen is not operationally practical.
Japanese Utility Model Application Publication No. 30484/1926 discloses a fountain pen in which a retaining metal member inserted into a tunnel-shaped guide formed in the pen body is placed on the upper surface of the nib and the retaining metal member is moved back and forth in association with the rotation of a rotary ring which is provided on the end portion of the holder cylinder. However, the fountain pen suffers from drawbacks in that the rotational direction of the rotary ring is different from the direction of movement (back and forth) of the retaining metal member, the force in the direction of rotation transmitted from the rotary ring is transferred through the guide to the pen so as to deform the pen, the resiliency of the pen is adversely affected by the presence of the guide, and it is difficult to manufacture the guide.
U.S. Pat. No. 2,669,970 discloses a pen construction in which the handwriting is varied by changing the nib's slit gap. However, the patent contains no teaching of a technique in which writing conditions are varied by changing the resiliency of the pen thereby to vary writing conditions. In the fountain pen of this patent, the pen and the valve are fixed so that they cannot slide and are engaged with the downwardly directed cam of the hood with the opening between the nib halves of the pen controlled by moving the shoulder of the pen back and forth with the cam. The valve does not affect the pen tip and the pen and the valve are fixed so that the pressure applied to the pen tip cannot be varied by moving the valve. In addition, the movement of the pen through the downwardly directed cam of the hood is through a very short distance, and therefore, although such movement may be effective, it may be able to control the opening of the pen but it cannot vary the elasticity of the pen. Thus, the fountain pen disclosed by the patent relates only to the control of the opening of the nib slit of the pen and with no capability of controlling the resiliency of the pen.
German Patent No. 727971, Austrian Pat. No. 42,731 and British Pat. No. 8277-02 disclose techniques for varying the resiliency of a pen tip by depressing the nibs although they do not relate to fountain pens. More specifically, in these patents, the rear portion of the retaining metal member is made cylindrical and the cylindrical portion is slidably inserted into the pen holder. These pens are disadvantageous in the following points. As a guide for guiding the retaining metal member is not provided, the retaining metal member is liable to move sideward. In addition, in a fountain pen of this construction, the cylindrical portion of the retaining metal member is positioned on the outer surface of the holder cylinder and therefore a cap covering the pen cannot be placed over the holder cylinder. Thus, these pens are not practical and could not be used as fountain pens.
Accordingly, an object of this invention is to provide a fountain pen in which all of the above-described difficulties accompanying conventional fountain pens have been eliminated.
A slit for introducing ink to the pen point is essential for a fountain pen. The writing conditions of the fountain pen are substantially determined by the resiliency of the pen tip in the region from the closed end of the slit to the pen writing point. Other essential factors affecting the resiliency are the structure of the pen body and the metal material of the pen and the length of the pen tip.
The resiliency of the tip is an important factor. The pen tip is divided by the slit into two parts as described above. The resiliency of the two nib halves and the spreading resistance between the two parts are also essential factors. If certain types of external forces are exerted on the pen, the nature of the pen may be adversely affected. Especially, torsional stress tends to fatally damage the pen and is to be avoided. Furthermore, a pen tends to be adversely affected by downwardly depressing the entire upper surface of the pen tip because in general this tends to cause the right and left parts of the pen head to become overlapped or to become staggered up and down.
A "closing action" of a pen tip is also desirable. A steel pen for clerical work may not only be worn out but also the point may open after only two or three days use because it has no "closing action" to hold the point together. The "closing action" is essential if a pen is to be used for several tens of years. The cross section of the pen tip is gently curved to provide such a "closing action" to the pen. If the entire upper surface of the pen is depressed, then such curves are eliminated and the "closing action" is defeated. If the entire upper surface of the pen is further depressed, then the ink will flow from the slit to the upper surface of the pen. If different forces are applied to the right and left parts of the pen tip, then the points of the right and left parts may become staggered and, at worst, the pen can no longer be used for writing.